The present invention relates to remote keyless entry types of systems employed with automotive vehicles.
Remote keyless entry systems are commonly used with automotive vehicles today. Such systems are including a wider range of functions that can be performed by the remote keyless entry system. For example, not only are the conventional lock, unlock, trunk release, and panic functions available, but also new functions such as remote engine start.
For certain functions, such as remote engine start, it is desirable to allow these functions to be performed while the operator is a greater distance from the vehicle than for some of the conventional functions. For example, one may wish to allow for the remote engine start, door lock, and panic alarm functions to be operable when the key fob is as far away from the vehicle as two hundred meters. To obtain this long rage functionality, the remote keyless entry system can be designed to operate at this greater distance.
Having the greater range of operation for the remote keyless entry system, however, may be undesirable for certain other remote keyless entry functions. One may wish to avoid inadvertently releasing the trunk if the trunk release button on the key fob is pressed when one is at this long range distance since he will not see or hear the trunk release. Moreover, one may not wish to inadvertently unlock the vehicle doors when at this longer range since one may be out of sight of the vehicle and thus not realize that the doors are unlocked. Accordingly, it may be undesirable for door unlock or trunk release functions to be operable from the same two hundred meter distance. Of course, the shorter range functions are still desirable for the remote keyless entry system, so operators may wish for these short-range functions to be operable only when the operator actuates the key fob at a more conventional range of, for example, about fifty meters or less.
Some have attempted to overcome this drawback by designing their remote keyless entry systems to try and detect the distance that the key fob is from the vehicle when the button is pressed, and then determine what function, if any, to perform based on this detected distance. This may be attempted by using received signal strength indicator (RSSI) circuitry. But due to environmental conditions, such as ambient radio frequency noise, this type of method can be very unrepeatable—that is, the range is not always consistently and accurately determined. Such inaccuracy may be undesirable for vehicle operators with these types of remote keyless entry systems. Thus, it is desirable to have a remote keyless entry system that allows for operation of both long-range and short-range functions, while overcoming the drawbacks of the prior art.